well im guessing the bottom isnt glazed. what probably is happening is when u put it in teh dishwasher or wash it, the bottom absorbs moisture then releases it into the substrate. if thats the problem leave it in the open for a cuople days or maybe put it in the oven on a really low temp.
other then that i have no clue
Only when the last tree has died, and the last river poisioned,
and the last fish caught
will we relize we cannot eat money.